lab-notebook-skills

Use when writing or editing source files inside an `experiments/expNN_*/eNNx/` cell directory, or about to add a `_lib/` / `utils/` / `helpers/` directory under `experiments/` — enforces root-canonical filename rule (cell source files must mirror project-root filenames), forbids shared helper directories, and gates function reuse to two options: import unmodified from root, or copy the entire root file into the cell and edit the copy.

Use when creating a new experiment directory, adding a variant cell, or tempted to rename / delete / edit a prior `experiments/expNN_*` directory — enforces next-unused-number rule, prior-experiments-are-read-only, variant naming `eNNa/b/c…`, and the principle that reservations are not free for re-use.

Use when designing a new experiment (read `experiments/NOTES.md` first to avoid repeating known-failed approaches), when a cell has finished and its metrics are committed (append an entry), or when correcting a wrong number in a prior entry (in-place fix is allowed and often required — leaving a wrong number on the page poisons future context; preserve the trail with strikethrough or a correction note when feasible, but accuracy of current evidence comes first) — enforces read-before-design, append-only-after-completion, every number traceable to an actual run (no estimates, no assumptions, no projected numbers), and root-cause hypotheses for every failed variant.